This invention relates to water heaters of the type which heat water that flows between two electrodes, rather than by providing a hot element which is contracted by the water. In this invention, the water is heated by electrical current flowing through the water when the water is between the two electrodes.
So called “instant” water heaters differ from conventional water heaters by their lack of a storage tank for hot water. Instead of heating and storing water for future usage, instant water heaters accept cold or cool water, heat it, and deliver it directly to the user point on demand. Such heaters find their most common usage in sink faucets, showers and tubes although they can be provided for any other usage that requires hot water.
Among their advantages is that they can be placed very near to the use point. Pipes of substantial length need not be emptied of cold water before hot water arrives from a central source for example. Also, it is much easier to run an electrical circuit to a distant heater than to provide a distant tank, or a long pipe to convey hot water from a central source to a distant use point.
Legionnaire's Disease is well known as a consequence of water stored for long periods at moderate temperature. Having no storage of the water at all profoundly reduces risk of such disease.
Presently-known instant water heaters do have major disadvantages, including short product life, dry-fire burn-out, short service life, liability to water damage, moderate rates of flow, high energy consumption, and release of metal ions into the water.
Another disadvantage of existing instant water heaters is their inability to accommodate varying input voltages and amperage along with water flow that matches their intended use. A complaint often heard is that the wrong instant water heater was purchased from among many different models. The necessary wide range of variables, such as voltage and circuit breaker amperage, and service flow in gallons is simply too confusing for many customers.
It is yet another disadvantage of existing instant water heaters that they often burn out or break coils due to water hammering, air in the water lines, or current overloads. These pose an electrical danger from direct contact of live broken coil ends to the water. The electrical current passes directly into the water. Manifolds that are connected to ground with a grounding wire corrode, and it is only a matter of time before a corroded manifold or a burned out coil releases a full current into the water and out a faucet or other plumbing fixture when in use, to the risk of the user.
It is a disadvantage of conventional electrode water heaters to have to contend with the wide variation of water conductivity of drinking water, both in the United States and in other parts of the world. Water conductivity is measured in microsiemens, which is the same as micro mhos. Mhos are the inverse of ohms, and therefore represent the conductive characteristics of water, which absorbs more power as it becomes more conductive. Water conductivity in the United States can range from 50 microseimens to over 1,500 microsiemens. Foreign countries can have as high as 1,800 microsiemens.
The disadvantage occurs when their electrodes must be sized such that they are capable of attaining satisfactory performance with 50 microsiemen water, but must then regulate a potentially hazardous 30 times the current draw when the water is at 1,500 microsiemens. For example, an electrode water heater on a 50-amp breaker must attain an acceptable performance of 40 degrees of temperature rise from its cold water inlet to its hot water outlet. If the water is conductive to 50 microsiemens and the heater passes 1 gallon per minute, the power required is 26.8 amps at 220 VAC. In this case, there is no disadvantage to using an electrode since this is below the current rating of its 50-amp breaker. If, for example the water conductivity is 1,500 microsiemens, the potential load would then become 804 amps. This power must be regulated to below the 50-amp circuit breaker and more specifically, to the 26.8 amps to meet the 40-degree temperature rise at 1 gallon per minute. The condition is exacerbated when 3 gallons per minute are required. The potential current draw for the flow rate is a staggering, 2,400 amps.
Since prior to this invention, electrodes could not be resized on the fly, regulating this amount of power has been costly. Typically, the common approach to electrode water heaters design is to use triacs, IGBT's, mosfets and other sine wave chopping devices to regulate the high current so that the circuit breakers do not trip. For low power requirements such as light dimmers, this is the preferred and inexpensive method. However, to regulate the high current potentials of electrode water heaters, these methods are economically and technically unacceptable.
It is yet another disadvantage of electrode water heaters that suggest methods of power regulation using said wave-chopping devices, that such devices can introduce harmonics in the line and heat the wiring without tripping the circuit breaker. Wires can become extremely hot, causing serious fire hazard. One solution to this disadvantageous condition is called “current matching”. However, current matching for electrode water heaters and boilers is nearly impossible to accomplish with such a widely varying electrical load without mechanically moving the electrodes as is done in large, expensive industrial electrode boilers. To do this in a home appliance such as an instant water heater would be too costly and would introduce wear parts that would greatly increase the failure modes of the device.
Yet another disadvantage of electronically regulating high current via AC wave chopping is the electromagnetic emissions that disrupt communications television signals and create radio static interference. These emissions are not allowed in Europe's “Flicker Standard” and can violate FCC regulations.
It is another disadvantage of electrode water heaters that in order to match the load to the line without the said expensive sine wave chopping devices, the preferred method is to physically move the electrodes via electric motors. This is done to either increase their relative distance from each other, or to pull them upward leaving less of the electrode submersed, hence reducing their surface area disposed in water.
It is an object of this invention to provide an electrode water heater whose current draw is passively and automatically regulated without chopping the sinusoidal AC electrical power which heretofore was necessary to regulate 1,500 amps, or more, down to within the required amperages of household circuit breakers.
It is another object of this invention to provide this regulation with no moving parts.
It is yet another object of this invention to accomplish this regulation with no electronic components such as triacs, IGBT's or mosfets sized to accommodate the high currents mentioned.
It is another object of the invention to regulate water temperature to an acceptable temperature by utilizing the merits of a Positive Temperature Coefficient conductive material that becomes a non-conductive at a preset temperature, and, where necessary, utilizing less expensive state of the art electronic technology for a finer temperature setting.
It is another objective of this invention to regulate water temperature by way of the water transferring its heat into the Positive Temperature Coefficient material, and rendering it, or some varying portion thereof non-conductive.
It is yet another objective of the invention to regulate a high inrush of current by way of the material's electrical resistance heating itself from within so that it, or some varying portion thereof becomes non-conductive so as to appropriately reduce the area of their opposed conductive faces.
It is yet another object of the invention to utilize the dynamic phase change location as a means to appropriately adjust the virtual effective size of the electrodes, in essence interpreting that dynamic as an electrode that passively and automatically changes its size to accommodate proper current draw and water temperature based on water conductivity and/or water flow.
It is another object of the invention to provide a temperature control valve disposed between the inlet and the outlet of the water heater's housing so as to provide a means to lower the outlet temperature of the water to below the PTC temperature of the material.
It is yet another object of the invention to restrict the flow of water through the water heater to a rate that will always allow for the PTC effect to render the electrodes non-conductive.
It is another object of this invention to regulate potentially thousands of amps with no electronic components. While the invention at first appears to defy the laws of physics by regulating its potential amperage draw without increasing its heat proportionally, as in the case of variable transformers, it must be understood that it is the load that is modulating itself. The result is a kinetic servo loop. The inverse occurs when the water's conductivity decreases, and an additional dynamic occurs when the flow of water acts upon the electrode's temperature. the complex dynamics of which will become apparent in the detailed description of the invention.